Intercommunication system



March 1o, 1942.

F. BERHLEY vINTERCOMMUNIGATION' SYSTEM Filed Dec. 14, 1939 3Sheets-Sheet l lvm March 10, 1942. F. BERHLEY 2,275,406

INTERCOMMUNICATION SYSTEM Filed Dec. 14, 1939 3 Sheets-Sheet 2 v v v v rf d J j Si o b b Q MN. NN- Nm U mw N\ .U num: .6265 @5.0mm mzaEm b wwl'. m,/r m m @Mw Si N .S a A?! 9 www mijn Nhvml am# 2E E@ 205.59V .3c@hw 6% March 1o, 1942. F. BERHLEY 2,275,406

INTERCOMMUNICATION SYSTEM Filed Dec. 14, 1939` 3 Sheets-Shea?l 3I"Illunumunnunil!l FED BER/MEV INVENTOR ATTORNEY messed-Mar. 1o, 1942INTERCOMMUNICATION SYSTEM Fred Berkley. Astoria', Long Island, N.v Y.,assignor of forty per cent to Maxwell E. Sparrow, New

York, N. Y.

Application December 14, 1939, Serial No. 309,202

14 Claims.

The present invention relates to intercommunication systems having aplurality of stations remotely located. According to this invention someof the stations hereinafter referred to as master stations are eachprovided with amplifying means having input and output circuits, earphone, loud speaker, change over switching means, earphone hook switch,selector switches speaker of the master as transmitter, amplifying y thesignal by the masters own amplifier and reproducing the signal in asecond masters earphone. Using the second masters loudspeaker as atransmitter, amplifying the signal by the second masters own ampliiierand using the'rst masters earphone as receiving means. Two waycomunication is thus established after selecting (push button orotherwise) and a light indicator system. Other stations, hereinafterreferred to as remote or sub-stations are each provided with loudspeaker, selector switch and light indicator means. The loud speakers inboth stations are preferably of the permanent magnet type having a voicecoil suspended in a permanent magnetic eld.

It is an object of this invention to completelyv eliminate side tones inintercommunicatlon systems; that is, when one master is communicatingwith another, neither master can hear its own signal in its ownreceiving means.

A further object of this invention'is to provide a selectivecontrollable. intercommunication system to enable interconnectedstations to communicate with each other without interference from eachother. A twisted cable is preferably provided to interconnect allstations.

lA still further object of this invention is to provide a lightindicating system throughout an f entire intercommunication system toindicate to operators of stations which station' desires to communicate,or which stations are communicating with each other.

Another object of this invention is to provide a novel buzzer to producean audible signal at .any station.

stations; likewise between master and remote stations, should it be sodesired.

A further object of this invention is to provide an intercommunicatonsystem having a plurality of operating advantages by using the same typeof master and remote stations for multiple operations.

The following give some of the operating advantages of this invention. ll

No. 1 master to masten-Using the loud by means of the selector switch,the second master. No further manipulation of any switches for thismethod of intercommunication is necessary.

No. 2 master to masten-A second method of operation, in a master tomaster hookup can be had by using the first masters loudspeaker astransmitting means by operating its change-over switch, and its earphoneas receiving means; and the second masters loudspeaker as a receivingmeans for receiving the signal from the rst master and as a transmitterfor transmitting tc the first master the second masterssignal with- Aoutthe second master manipulating any switches or controls. For thisoperation poweris supplied to the first master only.

No. 3 master to masten-Each master using its own amplifier and its ownloud speaker as either a transmitter or receiver by simply operating thechange-over switch on each master.

No. 4 master to masten-With the second master not touching any controlsor switches but with the rst master controlling the second masters loudspeaker circuit by its change-over switch, andthus providing thesecondmaster with either receiving or transmitting means, the firstmaster is able to receive the second masters signal either by earphoneor loud speaker. This operation becomes important if one vof the unitspower should fail during any other mode of operation.

No. 5 master to remota-Each master being able to communicate with eitherits own or with any remote station common toits own or any other master.The remote station having been i provided with a selector switch toinclude or exclude any masters signal. Also each remote station hasiight indicator means enabling it to be able to tell instantly whichmaster is` calling. The

master communicating with a remote is able to i receive the remotessignal either byl earphone or loud speaker. The whole operation ofreceiving and transmitting from any remote is controllable from anymaster connected to the particular remote station. y

No. 6 master to master as remota-The operation between a first masterand a second master can be 'hadl by operating the second master exactlylike a remote with the first master, by means of a change-over switch,controlling the loud speaker circuits of both the rst master and theremote master station. It is not necessary to supply power to theamplifier of the second master for this type of intercommunication.

For any type of intercommunication, other than No. 6l the lightindicator system of this invention will tell at a glance which master isoriginating a call and which master is responding. Also the lightindicator will also tell, in a master system having a plurality ofmaster stations, which two or more masters are in communication.

The above and further objects of the invention and the means for theirattainment will be more apparent from the following detaileddescription, taken in `connection with the accompanying drawings,illustrating an embodiment of which the invention may be realized, andin which:

Figs. 1 and 2 show the complete circuit diagram of 2 master stationswith provisions made for connecting two remote stations;

Figs. 3 and 4 show the circuit diagrams of said remote stations;

Fig. 5 shows the complete detail of an earphon hook switch;

Fig. 6 shows a change-over switch employable in the invention;

Fig. 7 shows in detail a method of mounting the earphone hook switch andthe change-over switch; Y

Fig. 8 is a rear view of a remote station selector switch; and.

Fig. 9 is a front View of Fig. 8.

The rotary selector switch shown in Figs. 8 and 9 is preferably aspecial type snorting switch.

one position 45B allows all masters connected to this switch to call theremote station and in other positions 65C, l35D, etc.'(Figs. 3, 4) toexclude any unwanted master station.

' The rotary selector switch shown in Figs. 8 and 9 consists of a singledeck of insulating material D with a number of contacts points I-II)mounted in front and in rear of the deck, a front and an opposite rearcontact being held together by means of a single rivet R andelectrically shorted together, with their common terminals 65A and lBjoined together by a conductor.

In the position shown in Figs. 8 and 9 the switches are in the allposition, meaning that any master connected to this switch at the pointsl-I, respectively, by means of an interstation conductor can call theremote station.l

If, then, a master calls a remote station the operator of the remote cantell by means of the indicator light which master is calling and maythen turn by means of shaft H of his switch S to the calling mastersconductor connected to one of the points l-i thus excluding all othermasters from communicating with this remote until remote has nished therst masters communication. The second master, however, can identify hiscall by flashing on his light indicator leaving on his light until theremote answers his call or if an urgent message must be transmitted tothe remote can identify his call by a series of pre-arranged flashes.

`lit is evident from the above and by an examination of Figs. 3 and 4.of the drawings that any remote, common to a number of masters isselective in respect to the masters, meaning that the remote can selectany masters incoming and any remotes outgoing signal; also any mastersoutgoing and any remotes incoming signal as far as master to remotestation operation is concerned.

Detail of the various operating methods y Figs. 1 and 2 show a completecircuit diagram of two masters and station .conductors to two remotestations. Figs. 1 and 2 are the two masters in normal or receivingposition, with power supplied to the masters, lever 8 in N or normalposition, all push buttons released or in out position and beingdesignated by the numerals 20, 2I, 22, L23, 24 and 25. The earphone I5is suspended from earphone hook switch 5. The weight of the earphonewill close leaves 5B and 5C.

The common terminal 1A of change-over switch 6 engages contact ICthrough feeder F and common terminal 'IE engages contact 1G throughfeeder F. A lever knob 8 is attached to shaft 8' of the change-overswitch 6.

The lever 8 carries a small extension rod or bar 'I'. A short piece ofelastic or felt material 'l is slipped over and fastened in place on rodor bar 'I'. This is done in order to prevent any clicks or mechanicalnoise being produced, when lever 8 is operated and in certain positionsstrikes the earphone hook 5. The amplifier 9 is a standard device withits own power supply indicated at I0, but not shown. The amplifier. hasbeen provided with an input transformer II-I8 and an output transformerI2-I3. The secondary of input transformer I1 connects with one side tothe ampliflers ground lead the other side of the secondary to the signalgrid of the first vacuum tube (not shown) of the amplifier. The primaryside of the output transformer I2 connects with one side .to the plateof the last or power tube (not shown) of the amplifier andthe 40' Thenumeral I4 indicates the loudspeaker dia-- phragm. The earphone I5 is ofa suitable impedance and the volume limiting resistor I6 is directlyshunted across the earphone and is lof a predetermined value. Thecondenser iI is of a suitable value and -is connected between the groundlead of the amplifier and the common conductor 9i, this being done inorder to eliminate stray coupling or capacity effects in theintercomrnunication system.

The selectors are shown as push buttons 2G, 2l, 2E and 23 of theconventional lock type holding their position when depressed and may bereleased by button 25. Button 28 is a simple spring return push buttonand is used for connecting feedback condenser I9 between the plate sideof the output transformer primary I2 to the signal grid input side ofinput transformer I 1A. Depressing button 24 will cause a certain amountof energy to be fed back from the output of the lamplifier 9 to theinput of the amplifier 9 and in audible note will be heard in any remotestation that may be connected to this master and selected by the stationselector push button. This constitutes the audible buzzer system. Pushbutton 24 -is independent of all other buttons.

Contacts 20A and 20C are mechanically coupled to button 20 thoughelectrically insulated from each other. Likewise 2IA and 2IC; 22A

pressed cause contacts between 20A- 20B and 20C-2 0D, simultaneously; 2IA-2 IB and 2 IC-2 ID, simultaneously; 22A-22B and 22C-2 2D,simultaneously, 22A-2 3B and 23C-23D, simultaneously.

Pressing push button 24 causes contact betweenV 24A and 24B. This pushbutton Varrangement provides station selection and light indication inthe present intercommunication system.

Terminal strip 50 carries the conductor` terminals 31, 3|, 32, 33, 34,35 and 36.

Contact points 20C, 2|C, 22C, 23C are connected in parallel and to oneside of the power line. Contact points 20D, 2ID, 22D and 23D alsoconnect in parallel but to one side of primary 26 of the light indicatorsupply transformer. The other side of primary 26 connects to the otherside of the power line. The secondary side 21 of the supply transformerconnects directly to a small rectifier 28 of the oxide type, havingsufficient capacity for the purpose intended. The negative side of therectifier connects directly to the common lead conductor 31. Thepositive side of the rectifier connects to one side of pilot lightindicator 29 and to terminal 32 on terminal strip 56 in Fig. 1 (masterstation No. 1); the

other side of indicator 29 connecting directly to common conductor 31.Pilot light indicator 30 also connects to the common 31 with one sideand with the other side to terminal 3| on terminal strip 50. Thisprovides the light indicator system for power line operation. If thissystem is to be battery operated then a suitable battery supply must besubstituted for transformer 26 vand 21 and rectifier 28 withthefollowing changes in wiring. The negative of the battery supply willhave to be connected to the common lead 31, buttons 20C, 2IC, 22C, 23Cbeing still connected in parallel but going to the'positive terminal ofthe battery supply, and buttons 20D, 2|D, 22D, and 23D still connectedtogether but connecting to the side of the pilot vlight indicator 29that formerly connected to the positive terminal of rectier 28. In Fig.2 (master station No. 2) the positive supply from either rectifier orbattery connects to one side of pilot light All stations areinterconnected by the following conductors. Conductor 31A from terminal31' of master station No. 1 (Fig. 1) to terminal 31' on master stationNo. 2 (Fig. 2) and to terminal C on remote stations Nos. 1 and 2 (Figs.

3 and 4). Conductor 3IA from terminal 3|. of master station No. 1 toterminal 3| of master station No. 2 and to terminal 42 of remotestawishes to call master station No. 2, it being, however, understoodthat power is supplied to both master stations.

Now, if the earphone I5 is lifted oi the earphone hook 5', leaf 5Acontacts leaf 5B. A conductor 65 connects 5A-5B to common terminal 1E onchange-over switch 6 through a common feeder F to contact points 1F and1G of switch 6 and from 1F--1G through conductor 66 to pushbuttoncontact 20B and from there through conductor 61 to terminal 33 on strip50 of master station No. 1, Conductor 33C connectsA master station No. 1to terminal 33 on master station No. 2. Conductor 68 connects terminal33 on master station No. 2 with pushbutton contact 2IB. Conductor 69connects contact 2IB with contact points 1G and 1F of switch 6 on masterstation No. 2 and through a common feeder F' to common terminal 1E ofswitch 6 on master station No. 2. The conductor 65 from 1E of masterstation No. 2 'continues toleaves 5B-5C of earphone hook 5 of master-station No. 2, leaf 5C being connected to leaf 5D, also throughconductor 1II to one side of the loudspeaker I4. The other side ofloudspeaker I4 connects to the common conductor 31 of master vstationNo. 2 then to terminal 31 on terminal strip 5U of master station No. 2,the common conductor 3| then retions Nos. l-and 2. Conductor 32B fromterminal '32 of master station No. 1 to terminal 32 of master stationNo. 2 and to remote station No. 1 terminal 4|; alsol remote station No.2 terminal 4| of conductor 32B from terminal 33 of master station No. 1to terminal 33 of master station No. 2. Conductor 34D from terminal 34of mas- `ter station No. 1 to terminal 34 of master station No. 2.Conductor 35E of master station No. 1 to 43 of remote station No. 1 andconductor 36F from terminal 36 of master station No. 1 to terminal 43 ofremote station No. 2. Conductor 36' from terminal 35 of master stationNo. 2 to terminal 440i remote station No. 1 and conductor 36' zfromterminal 36 on master station No. 2 to terminal 44 of remote stationNo.2.

Let it be assured that master station N6. 1 'la with the common lead 31.

turns to master station No. 1 through conductor 31A. Referring back toearphone hook 5 of master station No. 1, it is to be noted that leaf 5Ais connected to one side of theearphone I5, the other side of earphoneI5 connecting directly shunted directly across the earphone I5 at alltimes. Upon' lifting of earphone I5 from hook 5' leaf 5B disengages fromleaf 5C and engages or contacts with leaf 5A, leaf 5D making contactwith leafv 5E. Leaves 5C and 5D are connected together and byconductor`10 to one side of loudspeaker I4, the other side of theloudspeakery connecting with common lead 31. Leaf 5D having made contactwith leaf 5E now carries one side ofthe loudspeaker I4 through acoductor 1I to one side of the input transformer primary. I8 and tocontact 1D on change-over switch 6. The other .side of the inputtransformers primary I8 connects with the common lead 31. One side ofthe output transformer's secondary I3 connects with the common lead 31,and the other side thereof with contact points 1B, 1C, and1H on switch 6through conductor 12, the latter also connecting with a common feeder tocommon terminal 1A on switch 6 and with a conductor 13F to pushbuttoncontact points 20A, 2IA, 22A and 23A.

Depressing pushbutton 2| of master station No. 1 will close and lock inposition respective contact points 2|A-2IB and 2|C-2|D. A conductor 14connects contact point 2IB with terminal 34 on terminal strip 56 ofmaster station No. 1. Conductor 34D conects master station No. 1 withterminal 34 of master station No. 2, and continuing to pushbuttoncontact 2IB of master station No. 2, then through a conductor 69 tocontact points 1F and l1G on switch 6 of master station No. 2 andthrough common feeder F from contact point 1G to common terminal 1E,common terminal 1E through conductor 65 connects with earphone hook leaf5B, leaves 5C-,5D. Leaves 5C5D are connected together and throughconductor 10 to one side of loudspeaker I4 of master station No. 2. Theother side of loudspeaker I4 connects with common lead-31. Havingdepressedbutton 2| on master station No.

The resistor I6 isv 1 thus closing contacts 2IA-2IB and 2|C-2ID andapplied the power line voltage across the light indicator transformer'sprimary 26,-a secondary voltage is induced in secondary 21 and is fedinto the input of the oxide type rectifier 28. The negative terminal ofthe rectifier connects with the common lead 21. The positive terminal ofthe rectifier connects with one side of the pilot light 29 and toterminal 32 on terminal strip 50. In master station No. 2 the positiveside of the rectifier 28 connects with-pilot light 30, and with terminal3| on the terminal strip 50. Terminal 32 of master station No. 1

connects through conductor 32B with terminal 32 on master station No. 2and with one side of pilot 29. formers primary '26 in master station No.1 by depression button 2 I, will cause pilot light'29 thus closingcontacts 2IC and ZID in master station No. 1 and likewise pilot 29 inmaster station No. 2 to light up. If master station No. 1 now has itsbuzzer push button depressed an audible note will be heard in theloudspeaker of master station No. 2, due to the feed back capacity I9being connected to push button contacts 24A-24B and to input transformerside IIA. The pilot light constitutes this systems visual, and thebuzzer its audible, indication of a stations call. Now if the earphone Iof master station No. 2 is lifted off the hook 5' and the operator o fmaster station No. 2, knowing by prearrangement that his pilot 29belongs to master station No. 1, depresses his pushbutton 20, thusclosing pushbutton contacts A-20B and 20C-20D, he will cause his pilotlight 30 and pilot light 36 in master station No.A 1 to light up,indicating to master station No. 1 that master station No. 2 is readyfor communication, because the exact electrical action has taken placein master station No. 2 as has been described with relation to masterstation No. 1, when the earphone on master station No. 2 was lifted offthe hook.

To sum up, the: action which takes place in both masters are as follows:The loudspeaker of each master station is now used as a transmittingmeans and is placed across the input transformer of` each masterstations amplifier, but the output transformer I3 of master station No.1 is connected across the earphone of master station No. 2 and theoutput transformer VI3 of master station No. 2 has been connected-acrossthe earphone of master station No. 1. Two-way communication has thusbeen established without further manipulation of any switches. Whencommunication has been completed both masters press their respectiverelease buttons 25, and

-replace the earphones thus restoring the master stations tov theiroriginal or normal position and ready for another call.

It is evidentgfrom theY above vdescription that an`intercommunicationsystem has been provided with absolute privacy during communicationbetween two master stations and no other master station that may beconnected to the same system can possibly listen in. i It is alsoevident that the system is not limited to two master stations but bysimply adding interstation conductors, terminal posts, pilot lights,station selector pushbuttons, any number of master stations may beincorporated in an intercommunication system.

A second operation -with'the same master stations is possible, usingloud speaker to loud speaker between 2 master stations as describedheretofore in paragraph numbered 3. Again sta- Applyingva line voltageacross trans-.

tion selection must be'xnade by depressing and locking pushbutton 2|,after supplying power to both master stations and again pilot light 29will flash on in master station No. 1 and master station No. 2. Now theoperator of master station No. 1 does not have to lift the earphone I5of the earphone hook 5 but presses lever 8 on switch 6 into itslowermost position designated as T, or talk position and thereby liftsthe earphone hook, just high enough to again close leaves 5A and 5B andleaves 5D and 5E of earphone hook 5 by means of extension rod 'IIattached to lever 8. It is also evident that the conductor frompushbutton contacts 20A, 2|A, 22A and 23A and connecting to the commonterminal contact IA on change-over switch 6 and has been transferred bymeans of a common feeder F from contact 'IC to contact 'ID and to inputtransformer I8; also to leaf 5E and leaf 5D, leaf 5D having made contactwith leaf 5E, by pressing lever 8. Therefore loud speaker |4 beingconnected to leaf 5D has been placed against across the inputtransformers primary I8. When lever 8 was pressed into its lowermostposition T, common feeder F from common terminal lA moved away from 'ICto contact 1D and common feeder F1 from terminal IE moved away fromcontact `IG` to contact 1F, thus freeing contacts 'IB and 7C andcontacts 'IF and 1G. Contacts 'IH-'IB and IC being connected togetherand to output transformer I2 are now connected through common feeder Fto terminal 'IA and by a conductor '13, to pushbutton contacts 20A, 2IA,22A, and 23A; and having depressed and locked button 2| and therebyclosing contacts 2IA and 2 IB,

and continued from button contact 2IB through conductor 14 to terminal34 and by conductor 34D to terminal post 34 of master station No. 2 andon to button contact 2IB through conductor 69 of master station No. 2and to contact point 'IG through common feeder F to terminal point 'IEand by conductor B5 to leaf 5B through contact 5C and byconductor 10 toloud speaker I4 of master station No. 2. Both master stations beingconnected also by the common conductor 31A, it is evident that loudspeaker I4 of master station No. 2 is still placed across the outputtransformer I3 of master station No. 1. Master station No. 1 now useshis loud speaker as transmitting means and amplifying its signal bymeans of amplifier 9 reproduces its signal in loudv speaker I4 of masterstation No. 2. When master station No. 1 has nished a call, masterstation No. 2 operates lever`8 in the same manner as has justV beendescribed for master station No. 1. It is, of course, understood thatmaster station No. 1 has lever 8 returned to N or normal positionleaving button 2| depressed and locked until all messages have passedbetween the two master stations. If master station No. 2 depressesandlocks button 20 pilot light 30 will light up'in'both master stationsNo. 2 and No.1. Depressing lever 8 on master station No. 2 to thelowermost position results in the exact electrical action as has beendescribed for master station No. 1, except that master station No. 2uses loud speaker I4 for transmitting means and loud speaker I4 ofmaster station No. 1 as reproducing means for the amplified signal frommaster station No. 2 again through common conductor 31A and conductor33C from terminal 33 on master station No. 2 to terminal 33 on masterstation No. 1. Two-way loud speaker communication between two masterstations has thus been provided. It is also evident that either masterstation may receive the incoming signal either by earphone or loudspeaker, if so. desired and by operating the change-over switch asmentioned lsecond master station operating its controls or veven turningon its power. This operation becomes important if the power should failin any master station. With power supplied to master station No. 1pushbutton 2| is again depressed and locked in position. This againcloses conremote station is essentially the same as has been describedfor master stationv to master station l operation with the second masterstation not operating any controls. Remote stations may be connectedeither to respond to one `master station only or as shown in thedrawings. common to all master stations. Remote station No. 1 .connectsto master station No. l by means of conductors 35E. vcommon conductor31A and 34D to pushbutton contact 2 IB on master station No. 2 and tocontacts 'IG and IF on switch 8 of I master station No. 2, throughcommon feeder F to contact'IE and to switch leaf 5B closing throughcontact 5C loud speaker. lI4 to common conductor 3l on master stationNo. 2. Returning to master station No. 1 it is evident that theconductor v'I4 from pushbutton contact 2IB is carried, by previouslyhaving locked 2IA and 2IB, to terminal point 1A on switch 6, throughcommon feeder F to contact 1C, with contact IC connecting to outputtransformer I3 and to common'conductor 3l.l It is evident that loudspeaker I4 of master station No. 2 now has been placed across the outputtransformer of master station No. 1 and is used as the reproducer forany signal coming from master station No. 1. If lever 8 of masterstation No. 1 is now again pressed into4 `its lowermost position,earphone hook EI will be conductor 82B, master station No. 2 connects'also to remote station No. 1 by conductors 31A,

35 tand 3IA. Remote station No. 2 connects to master station No. 1 byconductors 31A, 32B and 86F. Master station No. 2 connects to remotestation No. 2 by means of conductors 31A, 8IA and 36'. If master stationNo. 1 wants to call remote station No. 1, the lever 8 of masterstationvNo. 1 must be pressed against into vits lowermost o r talkposition, button 22 must be pressed and locked in position; then loudspeaker 38 of remote station No. l will be placed across the outputtransformer I3 of master station No. 1 by means of conductors 31A and35E, contact 45D on switch 46 in remote station No. 1 and through itscommon terminals 45A and 45B.

. Pilot light.4ll will flash on by means of common conductor 81A and32B. Figures 38Aand38B only signify -start andflnish of speaker windingand have no other meaning. It should be mentioned that power must besupplied to a master station wishing to communicate with a remotestation. With switch S on the remote station in all positions as shown,it is entirely possible'for all malster stations to call the remotestation No. 1 at the same time. `While this feature is desirable it isnot entirely practical, for the following reason:

. Should remote station No. il be in .transmitting ter station No. 1 cannow transmit its signal to master station No. 2. In order to receive areply from master station No. 2, lever 8 of master station No. 1 must belifted to its uppermost or listen position L. The following takes place.The earphone hook 5' will be restored to normal position by weight ofearphone, common feeder F' will move from 'IG to 'IF thus placing loudspeaker I4 of master station No. 2 across the input transformer ofmaster station No. l and loudspeaker I4 of master station No. l acrossthe output transformer I2 of master station No. l. It is now clear thatby pressing lever 8 on mas- 1 ter station No. l into the lowermost ortalk position, master station No. 1 loud speakers will be used astransmitting means and loud speaker I4 of master station No. 2 will beused as reproducing means, and with lever 8 of -master station No. 1 inits uppermost or listenposition, loud speaker I4 of master station No. 2will be used as transmitting means'and loud speaker I4 of master stationNo. l will be used as reproducing means. 'I'he above confirms withparagraph 4, the buzzer operates in the usual manner by depressingbutton 25 and letting button return to normal.

` The next operation possible with this system, is in a master station'to remote station hookup as mentioned hereinbefore in paragraph numbered5. The operation between a master station and a position to masterstation No. 1 and master station No. 2 in transmitting position toremote station No. 1, the total output of master station No. 2 alongwith the signal from remote station No. 1 would appear at the input ofmaster station No. 1, resulting in such tremendous ampliiication, as toset up a howl or even render the whole system inoperative. Therefore,switch S has been provided to eliminate this. possible interference.When master station No. l calls remote station No. 1, the pilot light40, as stated before, will ash on and a buzzer signal will be heard inloud speaker 38 of remote station No. 1, informing the operator ofremote station No. l by visual means of pilot light 49 that masterstation No. l wishes to communicate.

or more master stations should it be necessary,y

by manipulating selector switch S and without interference from orbetween master stations. The same action as described for master station`No. 1, will take place-ifl master station No. 2

should call remote station No. 1, but then pilot light 39 will ash onand operator of remote,

station No. l must set his selector switch S to contact 45C in order toexclude any other master station. After nishing communication'with anymaster station, operator of remote station No. l returns his switch S tothe all position 45B e mote station No. 1.

n' rder to allow any master station to call re- It is evident from theabove descriptionl that the loud speaker 38 of any remote station isalternately used as transmitting and reproducing means, remotelycontrolled by switch 6 of any master station connected to the remotestation, land also that any master station in communication with anyremote station can receive the signal of the remote station at themaster station using either the earphone I or the loud speaker I4 of themaster station as reproducing means. After completing any call, releasebutton 25 must be pressed to restore all circuits to normal.

A still further type of operation possible with this system and asmentioned hereinbefore in paragraph numbered 6 is as follows: Masterstation No. 1 may call master station No. 2 operating master station No.2 as outlined before with l no power applied to master station No. 2 and0perating remote station exactly as outlined under master station vtoremote station operation with switch 6 and push-buttons 2l, 22 or 23 ofmaster station No. 1the controlling factor in this type of operation.Again the loudspeaker of master station No. 2 and the loud speaker ofany remote station are used alternately as reproducing and transmittingmeans.

Thus there has been provided an eiiicient intercommunication system withaudible and visual signals at remote master stations and remotesubstations. thus minimizing manufacturing and electrical difficulties,and with an unlimited amount of master and remote stations operation ina system without interference from and between each other.

It is, of course, understood that this system is' not limited to thenumber of master and remote stations shown in the drawings but may beextended to include any number of stations by adding additional selectorand light-indicator means, terminals, interstation conductors, pilotlights, etc.

In the accompanying drawings there is illustrated the invention embodiedin one of its practical forms but as this illustration is primarily forpurposes of disclosure it will be understood that the invention is notlimited to this vparticular form of structure and that it may bemodified in many respects without departure from the true spirit andscope of theinvention as herein defined and claimed. It is furtherunderstood that the terms which are employed herein are used in adescriptive rather than in a limiting sense, except, however, for suchlimitations that may be imposed by the state of the prior art.

Having thus described the invention what is claimed as new and desire tosecure by Letters Patent, is:

l. In an intercommunication system the combination including a pluralityof stations each station having loud speaker means, amplifying means andan earphone; means for using the loud speakermeans of each station as atransmitter, said amplifying means of one station for amplifying thesignal of said one station and simultaneously reproducing said signal inthe earphones of the remaining stations, means'for selecting forcommunication any one of the said remaining stations, and indicatingmeans for each of said stations for indicating the origin of a signalfrom any of said plurality of stations.

2. In an intercommunicating system the combination including a pluralityof stations each station having loud speaker means, amplifying means,station selector switching means, and switching means for transferringthe loud speaker means of one station from reproducing position totransmitting position and simultaneously reproducing the signal of saidone station in the loud speaker means of the remaining stations, meansfor selecting for communication any one of the said` remaining stations,,and indicating means for each of said stations for indicating theorigin of a signal from any' of said plurality of stations.

3. In an intercommunicating system the combination including a pluralityof stations each station having loud speaker means, amplifying means,switching means, means for alternately using the loud speaker means ofone station as its transmitter and as reproducer for the signal from theremaining stations, station selector switching means for selecting forcommunication any one or all of said remaining stations, and

indicating means for each of said stations fory indicating the origin ofa signal from A any of saidplurality of stations.

4. In an intercommunicating system the combination including a pluralityof stations each station having loud speaker means, at least one stationhaving .amplifying means, switchingl ing means in another position`conditioning the loud speaker of said selected station as a transmitterfor the amplifying vmeans of said one station and the loud speaker meansof said one station as reproducing means for the signal from the saidselected station, and indicating means for each of said stations forindicating theI origin of la signal from any of said plurality ofstations.

5. Inan intercommunicating system the combination including a pluralityof stations a first number of said stations having loud speaker means,amplifying means, earphone, earphone switch means and station selectorswitch means, a second number of said stations having loud speaker meansand station selector switch means, the station selector switch means ofone of said second number of stations being operable in one position forselecting an incoming signal from one of said first number of saidstations and an outgoing signal from said second number of said stationsto one of said first number of said stations and being operable inanother position for permitting communication between one of said secondnumber of said stations with one or all of said first number of saidstations.

6. In an intercommunicating system the combination including a pluralityof stationsa fi'rst number of said stations having loud speaker means,amplifying means, earphone, earphone switch means and station selectorswitch means, a second number of said stations having loud speaker meansand station selector switch means, the station selector switch means ofone of said second number of stations being operable in one position forselecting an incoming signal from one of said first number of saidstations and an outgoing signal from said second number of said stationsto one of said first number of said stations and being operable inanother position for permitting communication between a second number ofsaid stations having loud speaker means and station selector switchmeans, the station selector switch means of one of said second number ofstations being operable in one position for selecting an incoming signalfrom one of Asaid first number of -said stations and an outgoing signalfrom said second number of said stations to one of said first number ofsaid stations and being operable in another position for permittingcommunication between one of said second number of said stations withone or all of said rst number of said stations, indicating means forindi'catingin said one of said second number of said stations vwhichstations are communicating with each other or which of said first numberof said stations desires to communicate with said one of said secondnumber of said stations, and audible signall means for indicating tosaid station of said second number of said stations which of said firstnumber of said vstations desires to communicate with said station ofsaid second number of said stations.

8. In an intercommunicating system the combination including a pluralityof stations a first number of said stations having loud speaker means,amplifying means, earphone, earphone switch means and station selectorswitch means, a second number of said stations having loud speaker meansand station selector switch means, the station selector switch means ofone of said second number of stations being operable in one position forselecting an incoming signal from one of said first number of saidstationsand an outgoing signal from said second number of said stationsto one of said first number of said stations and being operable inanother position for permitting communication between one of said secondnumber of said stations with one or all of said first number of saidstations, indicating means for indicating in said one of said secondnumber of said stations which stations f are communicating with eachother or which ofv said first number of said stations desires tocommunicatewith said one of said second number of said stations, audiblesignal means for indicating to said station of said second number ofsaid stations which ofsaid rst number of said stations desires tocommunicate with said station of said second number of said stations,and conductorsconnecting said stations, said conductors including acommon conductor for receiving and transmitting.

9. In an `intercommunicating system the combination including twostations, each having amplifying-means, loud speaker means adapted to beused both as a receiver and a transmitter, an earphone and earphone hookswitch; a communication circuit between said amplifying means, loudspeaker means, earphones and earphone hook switches, said circuit,including interstation conductors connecting said stations with one ofsaid conductors acting as a common conductor for receiving andtransmitting, a second of said conductors completing the communicationcircuit between the amplifying means of one station and the receivingmeans oi the other station, and a third conductor completing thecommunication circuit between said other stations amplifying means andthe receiving means of said one station.

l0. In an intercommunicating system the corn-` bination including aplurality of stations, each having amplifying means, loud speaker meansadapted to be used both as a receiver and a transmitter, a stationselector switch, an earphone and earphone hook switch; a communicationcircuit between said amplifying means,

loudspeaker means, station selector switches,-

-ing means of one station and the receiving means of another station,and a third conductor completing the communication circuit between saidanother stations amplifying means and the receiving means of said onestation; and a change-overswitch for each station, said changeoverswitch being connected with earphone, earphone hook switch, loud speakermeans, amplifying means and to selector switch for selectively using theloud speaker means of said stations as receiving or transmitting means.

11. In an intercommunicating system the combination including stations,each having amplifying means, `loudspeaker means, earphone, an

earphone hook switch, a change-over switch a selector switch, and lightindicating means; a communication circuit between saidA amplifyingmeans, loud speaker means, station selector switches, earphones,earphone hook switches, said circuit including interstation conductorsconnectingv said stations with one of said conductors acting as a commonconductor for receiving, transmitting and indicating,` a second of saidconductors completing the communication circuit between the amplifyingmeans of one station and the receiving means of another station, a thirdconductor completing the communication circuit between said anotherstations amplifying means and the receiving means of said one station, afourth conductor completing the indicating circuit from one station tosaid another, and a fifth conductor completing the light indicatingcircuit from the said another station to the said one station, saidindicating means being operable simultaneously with the station selectorswitch to indicate which of the stations are in communication in thesystem.

12. In an intercommunication system, the combination including twostations, first and second respectively, a transmission circuit betweenthe rst station and the second station, a transmission circuit betweenthe second station and the first station, each circuit including a loudspeaker used as a transmitter, an earphone used as a receiver, anearphone hook switch, an amplifier, input means to said ampliner, outputmeans from said amplifier, and selector switch'means; said transmissioncircuits including a common conductor connecting with one side of theloudspeaker, earphone, output means and input means, the selector switchmeans of one of said stations for closing the transmission circuit ofthe other of said stations through its receiving means.

13. In an ntercommunicating system the combination including twostations, each having amplifying means, loudspeaker means adapted to beused both as a receiver and a transmitter; a communication circuitbetween said amplifying means and loudspeaker means, said circuitincluding interstation conductors connecting said stations with one ofsaid conductors acting as a common conductor for receiving andtransmitting, a second of said conductors completing the communicationcircuit between the amplifying means of one station and the receivingmeans of the other station, and a third conductor completing thecommunication circuit between said other stations amplifying means andthereceiving means of said one station.

14. In an intercommunicating system the combination including aplurality of stations, each having amplifying means loudspeaker meansadapted to be used both as a receiver and a transmitter, a stationselector switch; a communication circuit between said amplifying means,loudspeaker means and station selector switches, said circuit includinginterstation con-l plifying means and the receiving means of said onestation; and a change-overswitch for each station, said change-overswitch being connected with loudspeaker means, amplifying means and toselector switch for selectively using the loudspeaker means of saidstations as receiving or transmitting means.

FRED BERHLEY.

